SPECTRAL MODAL DYNAMIC ANALYSIS OF A REINFORCED CONCRETE BUILDING IN ACRE, BRAZIL

Resumo

This study presents a spectral modal dynamic analysis applied to a twelve-story reinforced concrete building located in the state of Acre, Brazil, a region that exhibits a moderate level of seismic activity due to its proximity to the Andean subduction zone. The analysis follows the guidelines established by the Brazilian seismic design code NBR 15421:2023, Design of Structures Resistant to Earthquakes. The building under study presents plan irregularities, resulting in eccentricities between the centers of mass and stiffness, which lead to torsional effects in the structure's dynamic response. A three-dimensional model was developed using the SAP2000 software, incorporating response spectra compatible with the seismic characteristics of the region. The adopted methodology includes the determination of natural frequencies and vibration modes, as well as the evaluation of the structural response under horizontal seismic excitations. Preliminary results highlight the influence of geometric irregularity on maximum displacements, redistribution of internal forces, and the identification of critical regions for structural design. This investigation contributes to the understanding of the dynamic behavior of buildings in areas of moderate seismicity in Brazil, providing guidelines for safer and more efficient design practices.